1. Field of the Invention
This invention relates to apparatus and methods to provide delivery of two or more fluids from an infusion pump.
2. Background of the Prior Art
The controlled delivery of liquids, particularly those containing medications, to patients has received substantial attention in the medical arts. The purpose of drug infusion is to give a patient medication intravenously over a known, usually prolonged, time period. Infusion eliminates the need for repeated injections and reduces the risk that the patient will develop drug sensitivities. Moreover, it is widely believed that sustained treatment with a drug is generally more effective than a single bolus treatment. Further, infusion pump devices allow for ambulatory treatment of a patient, i.e., the patient need not be attached to an intravascular ("IV") stand and bag.
There is often a need for infusion devices to deliver two or more fluidsto a patient. For example, infusion devices must typically be flushed clean after the medication has been dispensed. Sterile saline or occasionally a dextrose solution may be used for this purpose.
In addition, and more importantly for infusion devices using in-dwelling catheterization, once the flow of medication has ceased, the patient's blood may backflow into the infusion system. The blood eventually clots and blocks further flow through the system. For this reason, it is often desirable to maintain a gentle "KVO" (Keep Vein Open) flow of sterile fluid through the infusion system and into the patient, after all of the medication has been delivered. This KVO flow prevents any backflow and clotting. The KVO fluid may also include an anticoagulant such as heparin.
In other instances, it may be desirable to deliver two types of medication to the patient, either simultaneously or sequentially. There is a need for infusion systems having this capability.
A number of past products have been used to deliver a single fluid, such as medication, into a patient at a controlled flow rate. A typical example, which has been quite successful commercially, is illustrated in U.S. Pat. No. 5,080,652 to Sancoff, et al.
The relevant art has tended to focus on ambulatory care concerns. For example, many devices have been developed primarily for use by the patient, enabling him to administer the drug to himself or herself over a prolonged time without a hospital stay.
Devices such as the Sancoff, et al., product have been designed and intended for use shortly after preparation. The devices are filled with medication and soon thereafter connected to the patient, usually through an intravascular tube. The medication is then administered to the patient by the fluid flow and metering components of the particular device. For instance, in the Sancoff, et al. device the medication is delivered by elastic membranes which push the medication into the patient. Other devices, such as the one described in U.S. Pat. No. 5,106,374 to Apperson, et al. use compressed gas to force the medication from a container.
Some devices use chemicals that react to generate gas upon contact, providing on-the-spot pressurization. See, for example, U.S. Pat. No. 3,023,750 to Baron. The Baron device uses generated gas to force liquid from a bag for delivery to a patient.
However, none of these devices incorporate a means for delivering two or more fluids to a patient simultaneously or sequentially. In particular, none of these devices is capable of automatically flushing itself and its downstream intravascular lines clean. And none of these devices is capable of automatically providing a KVO flow of a different fluid, after the first fluid (the medication) has been delivered, to keep the intravascular lines open, or to provide a second liquid medication to the patient either together with or following infusion of a first liquid medication.
Thus, a need exists for a device which can be incorporated into a fluid infusion system to provide a simultaneous or sequential flow of two or more fluids to a patient.